fig6

Figure 6. Perforated human-device interfaces for e-skin system. (A) Wireless e-skin based on conventional IC chips (left) and the SAW sensor-integrated wireless e-skin (right) fabricated with GaN freestanding membranes; (B) Photograph of the SAW e-skin with a strain sensor attached onto the human wrist (left) and a strain measurement graph (right); (C and D) Optical microscopic image and schematic illustration of a GaN SAW device-based wireless ion sensor. Reproduced with permission from ref^[61]. Copyright 2022, AAAS; (E) Comparison of by-product removal effects in conventional and wearable patches. Reproduced with permission from ref^[62]. Copyright 2023, John Wiley and Sons; (F and G) Wearable e-skin with an eye pattern for enhancing the sweat removal property; (H) Sweat removal monitoring by eye-patterned e-skin and conventional one. Reproduced with permission from ref^[63]. Copyright 2023, Springer Nature; (I) Schematic illustration of the auxetic dumbbell hole pattern design for perforated e-skins; (J) 3D image of the sandwich-type e-skin fabricated with a PDMS-based adhesive layer, PI substrate layer, Au electrode, sensor semiconductor layer, and upper PI top layer; (K and L) Schematic illustrations of (I) auxetic dumbbell-patterned patch, (II) resistance-type thermometer, (III) Au-based capacitive hydration sensor, and ZnO thin-film-based (IV) strain and (V) UV sensor; (M) TEWL change after various e-skin lamination. Comparison of skin suitability of e-skin for one week. Strain sensor characteristics of the perforated e-skins and the conventional one according to skin dehydration and sweating. Reproduced with permission from ref^[64]. Copyright 2021, AAAS. IC: Integrated circuit; SAW: surface acoustic wave; 3D: three-dimensional; PDMS: polydimethylsiloxane; PI: polyimide; UV: ultraviolet; TEWL: transepidermal water loss.